Initial: Offchain Workers (#1942)

* Refactor state-machine stuff.

* Fix tests.

* WiP

* WiP2

* Service support for offchain workers.

* Service support for offchain workers.

* Testing offchain worker.

* Initial version working.

* Pass side effects in call.

* Pass OffchainExt in context.

* Submit extrinsics to the pool.

* Support inherents.

* Insert to inherents pool.

* Inserting to the pool asynchronously.

* Add test to offchain worker.

* Implement convenience syntax for modules.

* Dispatching offchain worker through executive.

* Fix offchain test.

* Remove offchain worker from timestamp.

* Update Cargo.lock.

* Address review comments.

* Use latest patch version for futures.

* Add CLI parameter for offchain worker.

* Fix compilation.

* Fix test.

* Fix extrinsics format for tests.

* Fix RPC test.

* Bump spec version.

* Fix executive.

* Fix support macro.

* Address grumbles.

* Bump runtime

substrate/core/service/src/config.rs

@@ -68,6 +68,8 @@ pub struct Configuration<C, G: Serialize + DeserializeOwned + BuildStorage> {
 	pub telemetry_endpoints: Option<TelemetryEndpoints>,
 	/// The default number of 64KB pages to allocate for Wasm execution
 	pub default_heap_pages: Option<u64>,
+	/// Should offchain workers be executed.
+	pub offchain_worker: bool,
 	/// Enable authoring even when offline.
 	pub force_authoring: bool,
 	/// Disable GRANDPA when running in validator mode
@@ -97,6 +99,7 @@ impl<C: Default, G: Serialize + DeserializeOwned + BuildStorage> Configuration<C
 			rpc_ws: None,
 			telemetry_endpoints: None,
 			default_heap_pages: None,
+			offchain_worker: Default::default(),
 			force_authoring: false,
 			disable_grandpa: false,
 		};